UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
934 of 1269
NXP Semiconductors
UM10503
Chapter 35: LPC43xx Real-Time Clock (RTC)
[1]
This register value is not changed by reset.
[1]
This register value is not changed by reset.
[1]
This register value is not changed by reset.
35.6.6.1 Leap year calculation
The RTC does a simple bit comparison to see if the two lowest order bits of the year
counter are zero. If true, then the RTC considers that year a leap year. The RTC considers
all years evenly divisible by 4 as leap years. This algorithm is accurate from the year 1901
through the year 2099, but fails for the year 2100, which is not a leap year. The only effect
of leap year on the RTC is to alter the length of the month of February for the month, day
of month, and year counters.
35.6.6.2 Calibration register
The following register is used to calibrate the time counter. The bits in this register are not
changed by reset.
Table 798. Day of year register (DOY - address 0x4004 6034) bit description
Bit
Symbol
Description
Reset
value
8:0
DOY
Day of year value in the range of 1 to 365 (366 for leap years).
31:9
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 799. Month register (MONTH - address 0x4004 6038) bit description
Bit
Symbol
Description
Reset
value
3:0
MONTH
Month value in the range of 1 to 12.
31:4
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 800. Year register (YEAR - address 0x4004 603C) bit description
Bit
Symbol
Description
Reset
value
11:0
YEAR
Year value in the range of 0 to 4095.
31:12
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 801. Calibration register (CALIBRATION - address 0x4004 6040) bit description
Bit
Symbol
Value
Description
Reset
value
16:0
CALVAL
-
If enabled, the calibration counter counts up to this value.
The maximum value is 131072 corresponding to about 36.4
hours. Calibration is disabled if CALVAL = 0.
-